Oleophilizing gelatinous images

ABSTRACT

Gelatinous images, especially lithographic materials having gelatinous images on metallic supports, for example, aluminum, are heated, for example, at 500* F. for 5 minutes, to render the gelatinous images durably oleophilic.

United States Patent Etter et al. 1 Mar. 21, 1972 [54] OLEOPHILIZING GELATINOUS [56] References Cited IMAGES UNITED STATES PATENTS [72] lnvemms gg g g i g z w Pamnelh 2,692,826 10/1954 Neugebaueretal ..9e/33 2,702,243 2/1955 Schmidt ..96/33 [73] Assignee: Eastman Kodak Company, Rochester, 2,763,553 9/1956 Clark et a1. ..96/33X NY. 3,053,658 9/1962 Spencer ..96/33 [22] Filed: July 1968 Primary ExaminerDavid Klein [2]] Appl. No 741,758 Attorney-W. O. l-lodson, P. R. Holmes and D. J. Holter [52] U.S.Cl ..96/33, 101/456, 101/467 [57] ABSTR CT [51] Int.Cl ..G03f 7/02 Gelatinous images, especially lithographic materials having [58] Field of Search ..96/33; 101/456, 467 gelatinous images on metallic supports, for example, aluminum, are heated, for example, at 500 F. for 5 minutes, to render the gelatinous images durably oleophilic.

3 Claims, 3 Drawing Figures T/ME (MINUTES) Patented Mar ch 21, 1972 3,650,742

F IG. 777] l [777i- GELAT/NOUS IMAGE mMMUALL/c SUPPORT F/ 2 /&

oumau OLEOPH/L/C /2/[ A WGELATINOUS IMAGE l0 METALLIC SUPPORT i T :--"r----r----" 5/0 540 570 600 630 660 690 720 TEMPERATURE Fl DOYLE 0. ETTER ANTHONY J. PAfiR/NELLO ma 22125 f OLEOPHILIZING GELATINOUS IMAGES This invention relates to photographic elements and processes. In one of its aspects this invention relates to lithographic printing plates. In another of its aspects this invention relates to methods and materials for the preparation of lithographic plates. In a further aspect this invention relates to lithographic plates having oleophilic gelatinous image areas on hydrophilic metallic supports and methods and materials for the production thereof.

Lithographic methods and materials are assuming an ever increasing role in the printing industry. The increasing demand for and use of lithographic products has been accompanied by consumer sophistication at a level which is difficult for the artisan to fulfill. The desire to satisfy the consumer requests and resultant artisan demands for better quality at reasonable production cost have stimulated vast research efforts to find plates which have a long press life, plate materials which require short exposure times and minimal detailed processing for plate preparation, and plates having wide press latitude.

The research efforts have, for example, resulted in lithographic support materials which are capable of functioning effectively for a large number of press copies. Metallic supports, such as aluminum or zinc, have been successfully employed. In recent years aluminum has been particularly attractive as a lithographic support material due in part to its cost, availability, and light weight. Efforts to utilize aluminum supports, however, with camera speed light sensitive materials which require minimal skill in processing, for example, light sensitive silver halide gelatinous compositions. have been fraught with difficulty. Extensive precautionary measures have had to be taken to avoid interaction of the aluminum support and the light sensitive materials. Even with these carefully manufactured plate materials excessive exposure times and highly skilled artisans were often required to convert the plate materials into useful printing plates.

The utilization of silver halide-gelatin compositions for long lasting plates has been a highly desirable goaldue at least in part to the low exposure time and minimal processing required for such compositions. Although silver halide compositions are particularly susceptible to environmental problems, some success has been achieved using such compositions together with aluminum supports, e.g., by separating the silver halide material from the aluminum with a plastic interlayer or by using a transfer system whereby light insensitive gelatin is imagewise transferred to metallic supports. It has nonetheless been difficult to prepare plates having gelatinous images which will retain oleophilicity and which are free of undesirable background and scum. The use of various methods to increase the oleophilicity, such as image conditioners, has been helpful but for the most part are of limited duration and often result in plates of limited press latitude which are not free of scum.

According to the present invention many of the above-mentioned prior art problems are obviated or minimized by utilizing a durably-oleophilizing quantity of heat to provide lithographic plates which have durably oleophilic gelatinous images.

Accordingly, the present invention provides photographic materials for use in preparation of lithographic plates having aluminum supports and durably oleophilic gelatinous images thereon.

The present invention further provides novel methods for the preparation of metallic printing plates having gelatinous images thereon which plates are substantially free of undesirable background.

In addition, the present invention provides methods for the preparation of lithographic plates having aluminum supports with gelatinous images of durable oleophilicity which methods can be effectively and consistently applied by relatively unskilled technicians. The resultant plates can be utilized directly on the press for long press runs with few if any of the precautionary measures which heretofore were required.

Furthermore, the present invention provides novel lithographic printing plates which may be effectively utilized for long press runs under varying press conditions and with a wide variety oflithographic inks, i.e., greasy printing inks.

Other embodiments and advantages of the present invention will be apparent from the following description taken together with the drawings. For a better understanding of advantages and specific objects derived by the practice of the present invention, reference may be had to the drawings in which:

FIG. 1 is an exaggerated cross section of a precursor to a lithographic plate according to one advantageous embodiment ofthe present invention;

FIG. 2 is an exaggerated cross section of the plate precursor of FIG. 1 after treatment according to one advantageous embodiment of the present invention; and

FIG. 3 is a chart indicating the quantity of heat which will render a gelatinous image durably oleophilic.

In one embodiment of the present invention as illustrated in FIG. 1, metallic support 10 comprises aluminum. Aluminum support 10 is provided with gelatinous image 12 in any suitable manner, for example, by gelatin image transfer to an aluminum support, by beginning with a light sensitive gelatinous layer on an aluminum support from which nonimage areas are selectively removed by etch bleach of washoff, etc. In addition to desired gelatinous image areas 12, plate precursors l6 frequently have undesirable areas 14, which ordinarily are ink receptive especially when treated with chemical image conditioners. This gives rise to undesirable background on the resultant prints.

To convert plate precursor 16 into lithographic plate 18 of FIG. 2, precursor 16 is exposed to a quantity ofheat which will render gelatinous image 12 durably oleophilic. Durably oleophilic gelatinous image 12 of FIG. 2 presents an ink receptive surface which will not lose oleophilicity even on long press runs. The exposure of precursor 16 to a durably-oleophilizing quantity of heat renders the use of image conditioning compositions unnecessary to the production of plates since the plate after heating is ready to put on the press. Surprisingly, the process according to the present invention results in plates which are substantially free from undesirable ink receptive deposits in nonimage areas. The specific fate of undesirable deposit 14 has not been fully ascertained. The absence of any material analogous to deposit 14 in plate 18 merely is a diagrammatic illustration that if there are any such deposits still present on plate 18 they are not ink receptive.

The chart of FIG. 3 indicates the quantity of heat which will render a gelatinous image durably oleophilic. Line 30 represents the approximate threshold heat level which must be attained to achieve durable oleophilicity. Heat levels substantially below threshold level 30 may give rise to superficial oleophilicity which may allow for some increase in desirable press characteristics of a plate but the effect is only temporary. Line 32 represents the approximate maximum quantity of heat tolerable before the plate loses some of its desirable characteristics. Although plates subjected to heat levels 38 which exceed 32 may be made to print, it is generally necessary to utilize image conditioner and a significant loss in press latitude is noted.

Between threshold level 30 and level 32 optimization of the process conditions may vary depending upon many factors including heating facility space, e.g., oven space, time, etc. Although in a highly advantageous embodiment of the present invention the plate precursor is converted into a useful plate by heating for about 5 minutes in an oven maintained at about 500 F., similar results may be achieved by heating at extremely high temperatures for very short periods of time, for example, by a high temperature flash. The latter approach gives rise to a greater flexibility in selection of support materials.

It should be noted that the temperatures and times which may be employed are to some extent dependent upon the support material selected, especially when the entire plate material is heated. Consequently, if support materials and subbing layers which cannot withstand the necessary heating are utilized, it is desirable to subject only the image side ofthe material to a high temperature flash so that the image gelatin may be durably oleophilized with minimal detrimental effect on the support.

The gelatin images as mentioned previously may be provided by any suitable method which results in an imagewise disposition of gelatin on a hydrophilic support. A particularly advantageous method of forming an image is to utilize a first brushed then phosphoric acid anodized aluminum support on which a photographic silver halide emulsion is coated, exposed to a light image, and developed in a developer such as Kodak Developer D-l9. Following development, the silver halide emulsion is immersed in an etch-bleach bath such as Kodak Etch Bleach Bath EB-4 containing cupric chloride, citric acid, urea and hydrogen peroxide. This results in bleaching silver grains and at the same time degrading or softening gelatin so that it is removed in the image areas. The resulting lithographic plate precursor is then heated to durably oleophilize the image and used on the press.

The photographic silver halide emulsions which can be used according to this advantageous embodiment of the invention include silver halide emulsions such as silver chloride, silver bromide. silver iodide, silver chlorobromide, silver chloroiodide, silver bromoiodide, silver chlorobromoiodide, etc. A particularly useful emulsion is a high contrast chlorobromide emulsion in which the silver halide contains at least 60 mole percent silver chloride.

Although it is preferred to use gelatin as the sole binding agent for the silver halide, it will be appreciated that other hydrophilic colloids can be used with gelatin to give a layer which can be hardened to a point where it has a melting point above about 180 F. and generally below about 300 F. Suitable hydrophilic colloids include colloidal albumin, cellulose derivatives, synthetic resins, particularly polyvinyl compounds and the like. Water insoluble polymerized vinyl compounds, e.g., polymers of alkyl acrylates or methacrylates, can also be included.

The coverage ofthe silver halide emulsion can be varied depending upon the use intended. A useful range is about 100 to 800 milligrams per square foot of gelatin, preferably 100 to 400 milligrams per square foot and about 50 to 200 milligrams per square foot of silver as silver halide, preferably 50 to 125 milligrams per square foot. The photographic emulsions described herein can be chemically sensitized such as with compounds ofthe sulfur groups, noble metal salts such as gold salts, reduction sensitized with reducing agents, combinations of these, etc. Furthermore, emulsion layers can be hardened with any suitable hardener such as aldehyde hardeners, aziridine hardeners, hardeners which are derivatives of dioxane, oxypolysaccharides, such as oxystarch, oxy plant gums, and the like.

The photographic silver halide emulsions can also contain additional additives particularly those known to be beneficial in photographic emulsions including, for example, stabilizers or antifoggants, particularly the water soluble inorganic acid salts of cadmium, cobalt, manganese, and zinc as disclosed in US. Pat. No. 2,829,404, substituted triazaindolines as disclosed in U.S. Pat. Nos. 2,444,605 and 2,444,607, speed increasing materials, plasticizers, absorbing dyes, and the like, Sensitizers which give particularly good results in typical emulsions useful in our invention are the alkylene oxide polymers which can be employed alone or in combination with other materials, such as quaternary ammonium salts as disclosed in U.S. Pat. No. 2,886,437 or with mercury compounds and nitrogen-containing compounds, as disclosed in US. Pat. No. 2,751,299. The emulsions can be blue sensitized, orthochromatic, panchromatic, infrared sensitive, etc.

The types of emulsions which may be employed according to the present invention, of course, include both negative and positive emulsions. Reversal emulsions or direct positive emulsions, such as hardened solarizing silver halide emulsions and hardened internal latent image silver emulsions forming the latent image mostly inside the silver halide grains, may in some instances be advantageously employed.

To increase sharpness, it may be desirable to include an antihalation pigment or dye in the emulsion. Typical dyes and pigments used in antihalation layers may be used provided they are inert to the emulsion and, when the etch-bleach system is utilized, do not affect the etch-bleach reaction. In a preferred embodiment, a carbon pigment is used. A useful amount of antihalation dye or pigment is 20 to 50 grams per silver mole.

It will be understood that the emulsion can be coated using methods known in the art. For the etch-bleach system of forming the plate image the emulsion must be sufficiently hardened so that it will have a melting temperature of at least about 180 F., generally above about 200 F. and preferably above about 230 F.

It will be appreciated that any ofthe conventional silver halide developing agents can be used in the practice of this invention. Such developing agents can be incorporated into the element contiguous to silver halide, e.g., in the emulsion layer or in a contiguous layer. Typical developing agents include hydroquinone and substituted hydroquinone, such as bromohydroquinone, chlorohydroquinone, toluhydroquinone, morpholinomethylhydroquinone, etc. It will also be ap preciated that an auxiliary developing agent can be used in an amount ofO to 20 percent of the hydroquinone or substituted hydroquinone in order to improve the speed without affecting the developing reaction.

Typical auxiliary agents include 3-pyrazo1idone, developing agents known in the art as well as Elon (N-methyl-paminophenol sulfate), and the like. Particularly useful auxiliary agents are l-phenyl-3-pyrazolidone and l-phenyl-4,4- dimethyl-3-pyrazolidone.

The developed silver halide emulsion advantageously is processed to a lithographic plate with an etch-bleach solution. Such solutions typically contain an oxidizing agent, such as hydrogen peroxide, an insoluble silver salt former, such as chloride ion, and a metal ion catalyst, such as cupric ion. A gelatin softener, such as citric acid and/or urea, may also be incorporated in the etch-bleach bath. The etch-bleach solution can be applied by spraying, dipping, immersing, swabbing, etc., in the areas where silver has been formed resulting in bleaching silver image and at the same time degrading or etching gelatin in these same areas. The etchbleach application normally removes the gelatin in the image area. However, the emulsion may be washed to remove the etch-bleach solution and any remaining softened colloid. If desired, the emulsion can then be re-exposed to regular roomlight and then redeveloped to provide an image in those areas which were not etched. This provides a darkened image area for proofing purposes on the plate. Of course, the emulsion can be hardened after the etch-bleach, if desired, to compensate for any surface softening due to the etch bleach. However, this is not necessary. The plate can be dried immediately following the etch-bleach operation heated to provide durably oleophilic gelatinous images and inked to provide a darkened image area and run on the lithographic press.

The etch-bleach solution may be one of those containing cupric chloride, citric acid, and hydrogen peroxide, such as Kodak Etch-Bleach Bath EB-3 or EB-4, as follows:

Kodak etch-bleach bath cb-3 Water, at F. EB cc. Cupric chloride 10g. Citric acid 10 g. Water to make 1 liter Hydrogen peroxide 3% 1 liter Kodak etch'hlcach bath EB-4 Water, at 125 F. 600 cc. Cupric chloride 10 g. Citric acid g. Urea 150 g. Water to make llter Hydrogen eroxide 3 percent 1 liter Another suitable etch-bleach bath containing copper sulfate, citric acid, potassium bromide and hydrogen peroxide is known as Kodak Etch-Bleach Bath EB-2. However, an etchbleach bath containing cupric chloride, citric acid, urea and hydrogen peroxide in which there is at least grams per liter of cupric chloride is particularly suitable in producing a clean removal of the gelatin in the image areas in a period of time as short as 20 seconds. Such etch-bleach solutions are described in Albert Sieg application Ser. No. 650,616, filed July 3, 1967. Various other oxidizing compounds may be used in place of hydrogen peroxide, such as hydrogen peroxide precursors and the like. However, oxidizing agents which are used in place of hydrogen peroxide must be those which act selectively on the image area where the silver image if located rather than attacking the complete emulsion layer which would be the case, for example, if nitric acid was utilized.

Although aluminum is a particularly useful support in the practice ofour invention, it will be appreciated that other supports can be used including metals such as copper, zinc, steel and the like which have been suitably hydrophilized or provided with hydrophilic surface. Similarly, other supports including paper, glass, various polymeric materials, such as polyesters, polyamides, polyolefins, and the like, may be used. Advantageously, the aluminum is anodized at least on the side which is to receive the light sensitive emulsion, desirably in accordance with the disclosure of Rauner et al., US. Ser. No. 567,031, filed July 1, 1966 and now US. Pat. No. 3,571,661 issued May 12, 1970. The aluminum may, however, be grained or brushed and optionally thereafter anodized. The emulsion is desirably coated directly on the support especially when the support is anodized aluminum.

The temperature-time relationship for the heating step employed according to the present invention is such that the heat employed will be sufficient to durably oleophilize the residual gelatinous image. The approximate minimum values of time and temperatures that may be satisfactorily applied according to the present invention are depicted by Formula 1.

I. r mp 157 wherein T represents temperature in degrees F. and

1 represents time in minutes such that the product ofthe temperature and time functions as indicated in the formula is at least about 157. The minimum temperature for satisfactory results is approximately 440 F. that is, 443 in the above formula. The maximum heat level tolerable in accordance with the present invention is important but varies more due to varying thicknesses of the gelatin image, impracticality of controlling high temperature levels accurately, etc. The maximum heat value employed for highly satisfactory results is represented by Formula ll. 5

T represents temperature in degrees F. and

1 represents time in minutes.

For ease in determination of the time and temperatures which may be satisfactorily employed, it is useful to use Formula III which describes level 32 of FIG. 3 and is an approximation of Formula ll, but stated in terms analogous to Formula l:

[11. (T-443)r 37l wherein T and r represent temperature and time above. I Thus, provided that the product of the temperature function (T-443) and time function (r'") is from about 157 to about 371. highly satisfactory results are obtained.

Accordingly; in one important aspect the present invention provides a process for the preparation of lithographic plates comprising providing a plate material having gelatinous compositions imagewise disposed on a metallic support, especially aluminum, and subjecting at least the gelatinous image to a quantity of heat for a sufficient period of time such that the product of the temperature function (T-443), wherein T equals temperature in degrees F. and is greater than 443 F., and the time function (t wherein t equals time in minutes is at least about 157 and no greater than 371.

The following examples are intended to illustrate the invention and/or advantages thereof but not to limit it in any way.

EXAMPLE 1 A phosphoric acid anodized aluminum support coated on one surface with a fine grain, high contrast silver chlorobromide gelatinous emulsion containing approximately 70 mole percent chloride of the type conventionally developed in a low sulfite hydroquinone lith developer is exposed, developed, etch-bleached and rinsed by conventional means. The resultant etch-bleached material is placed directly on a standard lithographic press. Attempts made to ink the plate and print from it result in no satisfactory prints even with inks of varying viscosity.

EXAMPLE 2 The procedure of Example 1 is followed except that before the etch-bleached material is inked the image is treated with an image conditioner as disclosed in 0.8. application Ser. No. 650,864, filed July 3, I967. Prints are obtained which have undesirable background especially with low viscosity inks, such as General Printing Ink, Web Offset Black.

EXAMPLE 3 The procedure according to Example 1 is followed except that before the etch-bleached material is put on the press it is heated for about 5 minutes in an oven maintained at about 500 F. The resultant plate is readily inked. When run on a press, the image appears durably oleophilic and produces in excess of 25,000 copies of excellent quality. The type of ink employed with this plate does not appear to significantly affect plate quality. High quality prints are obtained using: high viscosity inks, such as Speed King Jet Halftone Black, Interchemical Corporation; medium viscosity inks, such as Print Gloss Offset Black, Pope and Gray Company; and low viscosity inks, such as Web Offset Black, General Printing lnk Company.

EXAMPLE 4 The procedure according to Example 3 is followed except that the plate is heated at 500 F. for 20 minutes. Similar results are obtained. EXAMPLE 5 The procedure according to Example 3 is followed except that the material is heated at 500 F. for 30 minutes. On the press the plate tends to blind and does not produce acceptable quality prints. The support appears to have lost some of its desirable characteristics.

EXAMPLE 6 The procedure according to Example 3 is followed except that the material is heated at 500 F. for 4 minutes. On the press the plate inks up well and produces some acceptable prints but the plate tends to blind before 10,000 prints.

EXAMPLE 7 The procedure according to Example 3 is followed except that the material is heated at about 600 F. for about 3 minutes. Results similar to those of Example 3 are noted.

EXAMPLE 8 The procedure according to Example 3 is followed except that the material is heated at about 465 F. for about 60 minutes. Results similar to those of Example 3 are noted.

EXAMPLE 9 The procedure according to Example 3 is followed except that the material is heated at about 600 F. for about 1.5 minutes. Results similar to those of Example 3 are noted.

EXAMPLE 10 The procedure according to Example 3 is followed except that the material is heated at about 700 F. for about 0.6 minute. Results similar to those of Example 3 are noted.

EXAMPLE 11 The procedure according to Example 3 is followed except that the material is heated at about 800 F. for about 0.3 minute. Results similar to those of Example 3 are noted.

EXAMPLE 12 The procedure according to Example 3 is followed except that a grained or brushed aluminum support is utilized in place of the anodized aluminum support. Analogous results are achieved.

EXAMPLE 13 A gelatinous imagewise disposition is provided on a chemically grained aluminum support by a gelatin transfer system of the type disclosed in Clark et al.. US. Pat. No. 2,763,553. The resultant material is heated in an oven at 500 F. for minutes. The gelatinous image is thereby rendered durably oleophilic and possesses wide press latitude. Over 25,000 high-quality copies are obtained. No satisfactory copies are obtained when the same system is utilized with no heating step.

EXAMPLE 14 The procedure according to Example 3 is followed except that the material is heated at 400 F. for 3 hours. The plate initially inks up well but tends to blind after fewer than 10,000 copies.

The invention has been described in considerable detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention a described hereinabove and as defined in the appended claims.

We claim:

1. A process for preparing lithographic plates comprising:

a. providing a plate precursor having a gelatinous composition imagewise disposed on a hydrophilic support by: a. exposing to a light image a photographic element having a hydrophilic support and a hardened silver halide gelatinous emulsion coated thereover,

a. developing the element, and

a'. etch-bleaching the element to leave a gelatinous composition in imagewise disposition;

b. subjecting the etch bleached element to a quantity of heat such that the product of the temperature function (T- 443) and time function (r''") equals from about 157 to about 371 wherein T represents the applied temperature in degrees F. and to represent the period of time in minutes during which the composition is heated.

2. A process for preparing lithographic plates substantially free from undesirable ink-receptive deposits in nonimage areas comprising:

a. providing a plate precursor having a gelatino silver halide composition imagewise disposed on a hydroplilic support; and

b. subjecting at least the gelatino silver halide composition to heat such that the product of the temperature function (T-443) and time function equals from about 157 to about 371 as expressed in the formula:

(T-433) t"= 157 to 371 wherein Tis the temperature in degrees F. and l is the time in minutes.

3. The invention according to claim 2 wherein the support is anodized aluminum. 

2. A process for preparing lithographic plates substantially free from undesirable ink-receptive deposits in nonimage areas comprising: a. providing a plate precursor having a gelatino silver halide composition imagewise disposed on a hydroplilic support; and b. subjecting at least the gelatino silver halide composition to heat such that the product of the temperature function (T-443) and time function (t5/8) equals from about 157 to about 371 as expressed in the formula: (T-433) t5/8 157 to 371 wherein T is the temperature in degrees F. and t is the time in minutes.
 3. The invention according to claim 2 wherein the support is anodized aluminum. 